dipping tachometer

97 olds aurora. When decelerating slowly, the tachometer dips quickly, and lights dim. Car has stalled a few times. This only happens when decelerating slowly. If I break quickly, it doesn't happen. This just started after the fuel pump was replaced due to a recall. Took it back to the dealer and they cleaned and repositioned throttle plate, but it did not solve the problem. Any suggestions?

Check for a leak in your fuel pressure regulator.
The new pump may have put more pressure on
the diaphram and cracked it. There is a vacuum
line on the top of the FPR to just behind the
throttle plate. If the FPR diaphram gets cracked,
very often fuel will leak into the intake manifold
through this vacuum line and cause the mix
to be incorrect. Mine did the same thing for a
while, then started getting hard to start when
warm after sitting for about 10-15 minutes. It
was running way too rich.

If you pull this vacuum line off at the throttle plate,
you will see and smell fuel, if this is happening.
I suspect it is. Sounds exactly like what was
happening to me.